The present disclosure relates generally to the field of automated non-destructive inspection (NDI) of aircraft structural elements such as airfoil-shaped bodies, and more particularly to an automated NDI scanning apparatus that is coupled to and travels along an airfoil-shaped body having a relatively short chord length, such as a rotorcraft blade, an aircraft propeller blade, a winglet, a projectile fin, an aircraft horizontal stabilizer, etc., while performing a NDI function.
In order to inspect airfoil-shaped bodies such as blade components, it is known to manually remove the blade components from the aircraft and then manually perform the inspection function. Removal of blade components from an aircraft is cost intensive. With helicopter blades, for example, the time spent removing, transporting, re-attaching, balancing and trimming the blades can be significant. Some helicopters require that the blades be removed and inspected every 50-75 flight hours, resulting in a dramatically reduced mission capability of the aircraft.
Furthermore, performing NDI functions manually generally calls for using skilled technicians. These technicians are in short supply; therefore the labor cost to manually perform NDI functions is significant. Because manual NDI is complex and repetitive, the likelihood of human error is high. When a repetitive NDI operation is not performed properly by a human, a flawed blade component could be reattached to the aircraft.
Surface-riding probes in gimbaled holders have been used in the non-destructive inspection of composite aerospace hardware in some gantry-type systems. Such gimbaled holders typically comprise two gimbals, one mounted on the other with orthogonal pivot axes to allow the gimbal-suspended sensor show to rotate with two degrees of freedom. These systems generally require some level of “teaching” of the scanner to get close enough to the contour, and the gimbaling of the shoe handles the difference. They are usually using pulse-echo ultrasound, so the sensor or riding shoe can rest directly on the surface. Besides requiring “teaching”, these probes/shoes do not handle significant contours—like those on a rotorcraft blade leading edge—very well. One known scanning system has a spring-loaded shoe that works well for minor contours, but will not work for rotorcraft blades, particularly with sensors that have “contact feet” on them, because they tend to tip over.
Another apparatus for providing automated movement of a NDI sensor over a surface of an airfoil-shaped body is disclosed in U.S. Pat. No. 8,347,746. The apparatus in accordance with one embodiment comprises a “blade crawler” that travels in a spanwise direction along a rotorcraft blade. The blade crawler in turn has means for moving an NDI sensor in a chordwise direction. The respective movements in the spanwise and chordwise directions enable the NDI sensor to be rastered over the surface of the rotorcraft blade. The foregoing “blade crawler” automates what has been a slow and tedious hand-held inspection operation for rotorcraft blades, while allowing the rotorcraft blades to remain on the rotorcraft.
It would therefore be highly desirable to have an automated apparatus capable of scanning enabling a sensor array to inspect the entire surface area on one or both sides of an airfoil-shaped body in a single run along its length.